Fume hoods are well known in school and research laboratories to safely exhaust undesired reaction gases, vapors and other hazardous materials produced by chemical reactions effected within the reaction chamber. Herein, the reaction gases, vapors and other hazardous materials will be referred to collectively as "reaction gases". The necessary reagents and reactor vessels are placed in the chamber and the desired reactions occur manually as the reagents are mixed, etc. Gases produced by the reactions that are harmful and not needed in further reactions escape into the chamber to be exhausted therefrom together with the chamber ambient air by such as an exhaust fan through an opening at the back or top of the chamber. Fresh air enters the chamber through the front access opening by which the reactions manually are effected. Duct means external the fume hood conduct the exhausted gases and air for safe venting to the atmosphere or other equipment.
Previous fume hoods have been individually constructed and arranged for particular applications and have generally been designed for installation as a fixture in a laboratory room. For example, see U.S. Pat. No. 3,941,040 providing a special polygonal structure for a classroom environment in which a teacher supervises two students conducting chemical reactions in the same fume hood. The structure disclosed in that patent presents three openings for manual access that are tangentially arranged around a central mounting post that includes exhaust openings for removing the undesired reaction gases.
Typical prior fume hoods have rectangular work areas arranged to be in front of the student or research experimenter. This rectangular work area has a short depth in front of the experimenter and a sometimes more than ample width laterally of the experimenter. Typically, the depth is two feet and the width can be four to eight feet. This rectangular work area shape is believed to be inefficient use of space because of the limited depth in front of the experimenter and the experimenter having to reach or walk laterally to the extent of the width of the hood.
A minimum average linear rate of air movement through the access opening into the chamber must be maintained to guarantee confinement of the undesired gases in the fume hood chamber. A lesser rate of air movement can allow the gases to leak out through the access opening. The large openings of the prior fume hoods required large fans and motors moving large quantities of gases and air to obtain the minimum linear rate of air movement, which requires excessive energy and is noisy. A new fume hood desirable should move lesser quantities of gases and air while insuring proper fume hood gas retention.
Recently, robotic mechanisms that include a radially extending arm extending from a central pedestal or platform are being used in conducting chemical reactions in an enclosed fume hood environment. This presents new requirements for fume hoods. For example, where the reactions to be affected are particularly dangerous to humans, the fume hood should completely enclose the reaction chamber; the robotic mechanisms have substantially a circular reach around the pedestal and therefore the working area in the fume hood should be substantially circular; the fume hood should be readily configured of standard components to reduce the cost of designing and installing custom fume hood structures; and connection of the fume hood to external duct work for exhausting undesired reaction gases should be readily implemented.